Implementing Cisco IP Switched Networks (SWITCH v2-0) (#160)

You have recently deployed an access switch with two fiber cables that connect it to a distribution switch in EtherChannel mode. Soon after it booted up, one of the uplink ports to the distribution switch was error-disabled. Which option is the most likely reason for the problem?

The switch is operating in UDLD aggressive mode and it failed to receive a UDLD message from the peer.
The port-channel detected an inconsistent configuration.
The switch is operating in UDLD normal mode and it failed to receive a UDLD message from the peer.
Spanning tree is detected a loop.